Gliederung

Objective: State of the art intensive care for SAH and TBI patients relies to a certain degree on neuromonitoring data including local brain tissue pO2 measurements. Usually local pO2 probes are placed in the white matter around 2 cm below the cortex. Here we compare a opto-chemical method of planar oxygen detection for measuring changes of cortex pO2 to an intraparenchymal Licox probe during a reversibly introduced epidural mass lesion.

Methods: 9 male Wistar rats (m = 305 Â± 22 g) were sedated (midazolam, fentanyl, medetomidine), intubated and ventilated. A cortical window was prepared with a translucent porphyrine containing sensor foil. The sensor was excited by short light pulses (λ= 405 nm) and pO2 dependent light emissions were recorded with a CCD camera of the measurement device (Biocam, Regensburg). A balloon device, which simulated an epidural mass lesion, was placed over the contra lateral hemisphere. Throughout the experiment, the balloon was inflated up to an ICP of approx. 40 mmHg for 60 minutes and then deflated. Licox pO2, cortex pO2, ICP, RR, body temperature, EEG and cortex pO2 were recorded and blood gas samples were drawn.

Conclusions: Cortical pO2 values and Licox/white matter pO2 appeared to be weakly correlated, while absolute values differed. In some sections of the experiment, a completely different behaviour of the two probes was observed. Measuring cortex pO2 appears to be complementary to the detection of white matter pO2 and may serve as an additive neuromonitoring tool for selected cases.